EP0078653B1 - Circuit à modulation angulaire - Google Patents

Circuit à modulation angulaire Download PDF

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Publication number
EP0078653B1
EP0078653B1 EP82305681A EP82305681A EP0078653B1 EP 0078653 B1 EP0078653 B1 EP 0078653B1 EP 82305681 A EP82305681 A EP 82305681A EP 82305681 A EP82305681 A EP 82305681A EP 0078653 B1 EP0078653 B1 EP 0078653B1
Authority
EP
European Patent Office
Prior art keywords
transistor
emitter
resistor
voltage
base
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
EP82305681A
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German (de)
English (en)
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EP0078653A1 (fr
Inventor
Kenichi Hasegawa
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Panasonic Holdings Corp
Original Assignee
Matsushita Electric Industrial Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
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Publication date
Application filed by Matsushita Electric Industrial Co Ltd filed Critical Matsushita Electric Industrial Co Ltd
Publication of EP0078653A1 publication Critical patent/EP0078653A1/fr
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Publication of EP0078653B1 publication Critical patent/EP0078653B1/fr
Expired legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03C—MODULATION
    • H03C3/00—Angle modulation
    • H03C3/02—Details
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N5/00—Details of television systems
    • H04N5/38—Transmitter circuitry for the transmission of television signals according to analogue transmission standards
    • H04N5/40—Modulation circuits

Definitions

  • This invention relates to a circuit which angularly modulates a composite video signal, and more particularly to a circuit in which the width of frequency deviation and the lower limit of frequency deviation can be adjusted independently.
  • the conventional circuit for angle modulation of a composite video signal has such a drawback that when the width of frequency deviation is changed or adjusted the lower limit of frequency deviation varies.
  • Fig. 1 shows a conventional circuit. The above-mentioned problem will be discussed in more detail with reference to the figure.
  • a video signal supplied from a signal source SG 11 is voltage divided by a variable resistor VR 11 and supplied to an amplifier circuit A 11 through a capacitor C " .
  • the output video signal of the amplifier circuit A 11 is supplied to the base of a transistor Q a through a capacitor C 12 .
  • the voltage V 11 of a voltage source V 11 is supplied also to the base of the transistor Q a through a switch SW " .
  • Fig. 2 is a diagram showing the timing relation between the opening and closing of the switch SW " and the video signal. In Fig. 2(a) the ordinate indicates the base voltage V B-Qa . of the transistor Q a , while in Fig.
  • V B-Qa of the transistor Q a is expressed by where V SG11 (t) denotes the voltage of the video signal supplied from the signal source SG11, that is, the value of voltage at a time t with the voltage of sync-tip referred as OV.
  • the collector current Ic-o a of the transistor Q a may be given by if the current gain h FE is sufficiently large.
  • the value 0.75 V is the voltage drop between the base and the emitter of the transistor Q a which is in active state.
  • the collector current Ic-o a of the transistor Q a is conducted to a variable frequency oscillator VCO, and a frequency modulated signal is derived from an output terminal T OUT .
  • Fig. 3 shows the relation between the oscillation frequency of the variable frequency oscillator VCO and the current I C-Qa .
  • the ordinate above the origin is the oscillation frequency Freq and the abscissa is the current I C-Qa .
  • the ordinate below the origin expresses the time t.
  • the oscillation frequency Freq and the current Ic-o a have the following relation.
  • K is a constant. It is so adjusted that the level of the video signal in the sync-tip period corresponds to a lower limit f, of the frequency deviation while the white level corresponds to an upper limit f u of the frequency deviation.
  • the variable frequency oscillator VCO need not be any special circuit.
  • a voltage controlled multivibrator as disclosed in Japanese Patent Application No. 51-85313 (No. 85313/76) by the same assignee of the present application may be applied.
  • Fig. 4 shows the variable frequency oscillator, where transistors 1 and 2, and 3 and 4, constitute differential switching circuits which switches the collector current l o of the transistor Q a and the current of a current source formed by a transistor 5 and a resistor 7.
  • a terminal 36 is connected to a voltage source V ss .
  • R a and 7 denote resistors.
  • the transistor Q a and the resistor R a which was already shown in Fig. 1 are surrounded with a broken line.
  • Resistors 8 and 9 are connected to the collectors of the transistors 3 and 4, respectively.
  • a capacitor 12 is connected to the emitters of the transistors 10 and 11.
  • Transistors 13, 14 and 15,16 constitute voltage comparators which compare the voltage across the capacitor 12 and the emitter voltage of a transistor 17.
  • Resistors 18 and 19 divide the voltage of a power source +B' in order to supply a reference voltage to the comparator circuits.
  • the values of current of the current sources 20 and 21, which are constituted with a resistor and a transistor, are equal to each other.
  • a current source 22 supplies an appropriate value of current.
  • Transistors 29 and 30 form a flip-flop circuit in which 31 and 32 are input terminals and 33 and 34 are output terminals having opposite phases to each other.
  • the function of the flip-flop circuit is as follows.
  • the output terminals 33 and 34 have low and high levels, respectively. Even if the collector current of the transistor 13 rises above the predetermined level thereafter, the output states are held until the collector current of the transistor 14 falls below a predetermined level. Furthermore, if the collector current of the transistor 14 falls below the predetermined level, the output terminal 33 is turned to the high level and the output terminal 34 is turned to the low level.
  • the output state is held until the collector current of the transistor 13 falls below the predetermined level.
  • the base voltage of the transistors 10 and 11 can be equal to the voltage +B' or smaller than it because of a voltage drop due to the current of the current source 5 flowing through the resistor 8 or 9.
  • the lower voltage level due to this voltage drop is set to be equal to a value high enough that either the transistor 10 or 11 does not become conductive just before the emitter voltage of the transistor 10 or 11 drops to reverse the flip-flop. It is desirable that the emitter voltage of the transistor 10 or 11 at which the flip-flop begins to reverse is set to be equal to the emitter voltage of the transistor 17 in order that the temperature drift compensation can be made more perfectly.
  • the transistor 17 performs the temperature compensation for a temperature drift of the transistors 10 and 11. Since the transistors 13, 15 and 14, 16 are connected in such a manner that the temperature drift of the forward voltage between the base and the emitter can be compensated, the voltage swing across the capacitor 12 does not vary with the temperature drift.
  • the collector current l o of the transistor Q a is determined by an input voltage applied to the base input terminal 35 and the resistor R a .
  • the temperature drift in l o can be minimized by externally connecting as R a a carbon film resistor or a metal film resistor with a small temperature drift coefficient to the main semiconductor IC, since the temperature drift of the forward voltage between the base and the emitter of the transistor Q a can be easily compensated by its base bias.
  • the frequency of oscillation output becomes stable against any temperature variation.
  • three terminals i.e. the both ends of the capacitor and the connection terminal of R a , can serve as the connection terminals to the exterior of the IC.
  • the switching section of the flip-flop circuit is constituted with transistors 23 and 24.
  • Transistors 25 and 26 are provided for the purpose of positive feedback.
  • the input terminals of the flip-flop circuit receive the output of the voltage comparators, and supplied through transistors 27 and 28.
  • a d.c. bias source is connected to a terminal 36 to feed the current sources.
  • the source voltage +B' is made a little lower than the source voltage +B.
  • the oscillation frequency Freq of the signal . derived from the output terminal Tour (34) in Fig. 1 may be expressed from eqs. (1), (2), and (3) as
  • the second term of eq. (4) expresses a variation due to the video signal input V SG11 (t), which becomes maximum at the white level and OV in the sync-tip period.
  • the frequency deviation of the oscillation frequency tends to the upper limit in thu white level, while it tends to the lower limit in the sync-tip period.
  • the resistance of the variable resistor VR 11 is varied, the voltage of the white level of the video signal V SG11 , (t) changes, whereby the width of the frequency deviation is varied.
  • the value of the resistor R a in Fig. 1 is varied in order that the lower limit value of the frequency deviation of the frequency modulation may be set at a predetermined value f, not only the first term of eq. (4) but also the second term of eq. (4) varies. Namely, the width of frequency deviation varies.
  • the most important point of adjustment in the prior art of Fig. 1 becomes as follows: the first step is to vary the value of the resistor R a to set the lower limit of frequency deviation at f, and the second step is to vary the value of the variable resistor VR, 1 to set the width of frequency deviation at (f u -f l .
  • This order of adjustment should not be reversed. Therefore, in the adjustment process of a mass production line or when some repair becomes necessary due to the appearance of inferior components or when the values of f u and f, must be changed as desired, there occurs a problem that no careless mistake can be allowed in the order of adjustment.
  • the objective of this invention therefore is to provide a circuit for angularly modulating a composite video signal, in which the setting of the width of frequency deviation and the setting of the lower limit frequency deviation can be done independently from each other.
  • a first transistor constitutes an emitter follower where a first resistor is connected with the emitter.
  • the base of the first transistor is connected to a signal source of the composite video signal through a capacitor and also to a second voltage source through a switch.
  • the base of a second transistor is connected to the second voltage source and its emitter is connected to a first voltage source through a second resistor.
  • the emitter of the first transistor and the emitter of the second transistor are connected with each other through a third resistor.
  • the collector current of the second transistor is supplied to a variable frequency oscillator.
  • variable frequency oscillator VCO is the same as used in Fig. 4.
  • Transistors Q b and Q c shown in Fig. 5 are connected in place of the elements as shown in the broken lines in Fig. 4.
  • a video signal supplied from a signal source SG 1 is supplied to the base of the transistor Q 1 through a capacitor C 1 .
  • the voltage V 2 of a voltage supply V 2 is also supplied to the base of the transistor Q 1 through a switch SW,.
  • the emitter of the transistor Q 1 is connected to a voltage source V 1 through a resistor R 1 .
  • the emitter of the transistor Q 2 is connected to the voltage source V, through a resistor R 2 while its base is connected to the voltage source V 2 .
  • the collector of the transistor Q 2 is connected to the collector and the base of the transistor Q b .
  • the base and the emitter of the transistor Q c are connected to the base and the emitter of the transistor Q b , respectively.
  • the collector of the transistor Q c is connected to the variable frequency oscillator VCO (e.g., by substituting the block including Q b , Q c for the block including Q a respectively indicated by broken lines in Fig. 4).
  • the transistors Q b and Q c constitute a current mirror circuit.
  • the switch SW 1 is closed only in the sync-tip period of the video signal.
  • the capacitor C 1 , the switch SW 1 and the voltage source V 2 operate in the similar manner as the capacitor C 12 , the switch SW 11 and the voltage source V 11 in Fig. 1, respectively.
  • the base of the transistor Q 1 is supplied with the video signal with its sync-tip voltage clamped at the voltage V 2 .
  • the transistor Q 1 acts as an emitter follower with the resistor R 1 .
  • the base voltage of the transistor Q 2 is equal to the voltage V 2 .
  • the current I E-Q2 flowing into the emitter of the transistor Q 2 is given by a sum of a current I R2 flowing from the voltage source V 1 through the resistor R 2 and a current I R3 flowing from the side of the transistor Q 1 through the resistor R 3 .
  • the current I R2 is given by where the valu e of 0.75 V is the voltage drop between the base and the emitter of the transistor Q 2 (and Q 1 ) which is in active state.
  • V E - 02 of the transistor Q 2 is given by Due to the clamp action of the capacitor C, and the switch SW1, the emitter voltage V E-Q1 of the transistor Q 1 is expressed as where V SG1 (t) denotes the voltage of a video signal supplied from the signal source SG1 with the sync-tip part expressed as OV.
  • the current I R3 flowing through the resistor R 3 becomes Thus, the emitter current I E - 02 of the transistor Q 2 becomes If we assume that the current gain h FE of the transistors Q 2 , Q b and Q c are sufficiently large, the collector current I C-QC of the transistor Q c becomes equal to the emitter current I E - Q2 of the transistor Q 2 . If the variable frequency oscillator VCO is the same as the one shown in Fig. 1, the oscillation frequency Freq is expressed as The first term of eq. (10) corresponds to a level variation of the input video signal and indicates that changing of the resistance of resistor R 3 is equivalent to a change of the video signal level.
  • the order of setting the lower limit frequency f l of frequency deviation and the width thereof (f u ⁇ f l ) in the frequency modulation circuit can be done arbitrarily. Namely, the lower limit frequency f, can be adjusted by the resistor R 3 while the width of frequency deviation (f u ⁇ f l ) can be adjusted by the resistor R 4 .

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  • Engineering & Computer Science (AREA)
  • Multimedia (AREA)
  • Signal Processing (AREA)
  • Television Signal Processing For Recording (AREA)

Claims (5)

1. Circuit de modulation angulaire, comprenant un premier transistor (Q1) qui comporte un émetteur, une base st un collecteur, sa base étant montée de manière à recevoir un signal vidéo composite à travers un condensateur (C1), une première et une seconde sources de tension constante (V,, V2), une source de courant raccordée à l'émetteur du premier transistor (Q1), un interrupteur (SW,), reliant la base du premier transistor (Q1) à la seconde source de tension constante (V2), un second transistor (Q2) qui comporte un émitteur, une base et un collecteur, sa base étant raccordée à la seconde source de tension constante (V2), une première résistance (R2) reliant la première source de tension constante (V,) à l'émetteur du second transistor (Q2), une seconde résistance (R3) reliant l'émetteur du premier transistor (Q1) à l'émetteur du second transistor (Q2) et un oscillateur à fréquence variable (VCO) réagissant au courant de collecteur du second transistor (Q2), de telle manière que la fréquence limite inférieure puisse être réglée par la première résistance (R2), tandis que l'étendue de la variation de fréquence peut être réglée par la seconde résistance (R3), chacun de ces réglages étant indépendant de l'autre.
2. Circuit de modulation angulaire selon la revendication 1, dans lequel l'interrupteur (SW1) n'est fermé que dans la période d'un signal de synchronisation horizontale du signal vidéo.
3. Circuit de modulation angulaire selon la revendication 1, dans lequel le courant de collecteur du second transistor (Q2) est délivré à l'oscillateur à fréquence variable (VCO) à travers un circuit miroir de courant.
EP82305681A 1981-10-27 1982-10-26 Circuit à modulation angulaire Expired EP0078653B1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP56172314A JPS5873286A (ja) 1981-10-27 1981-10-27 角度変調回路
JP172314/81 1981-10-27

Publications (2)

Publication Number Publication Date
EP0078653A1 EP0078653A1 (fr) 1983-05-11
EP0078653B1 true EP0078653B1 (fr) 1985-08-28

Family

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EP82305681A Expired EP0078653B1 (fr) 1981-10-27 1982-10-26 Circuit à modulation angulaire

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US (1) US4531155A (fr)
EP (1) EP0078653B1 (fr)
JP (1) JPS5873286A (fr)
DE (1) DE3265879D1 (fr)

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS62243406A (ja) * 1986-04-16 1987-10-23 Nec Corp 角度変調器
JP2650108B2 (ja) * 1988-03-18 1997-09-03 株式会社日立製作所 Ｆｍ変調回路
US7015766B1 (en) 2004-07-27 2006-03-21 Pericom Semiconductor Corp. CMOS voltage-controlled oscillator (VCO) with a current-adaptive resistor for improved linearity
JP7259343B2 (ja) 2019-01-18 2023-04-18 トヨタ自動車株式会社 配車サービスシステム、配車サービス方法、およびプログラム

Family Cites Families (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3214706A (en) * 1962-01-09 1965-10-26 Burroughs Corp Wide band amplifier with adjustable d.c. output level
NL294325A (fr) * 1962-07-02
US3263190A (en) * 1963-11-19 1966-07-26 Rca Corp Frequency modulated oscillator
DE1218525B (de) * 1964-11-07 1966-06-08 Telefunken Patent Verstaerker mit umschaltbarem Verstaerkungsgrad
US3512109A (en) * 1967-03-24 1970-05-12 Fowler Allan R Phase angle modulator
US3626331A (en) * 1969-01-14 1971-12-07 Motorola Inc Audio signal processor
US3626330A (en) * 1970-01-15 1971-12-07 Itt Capacitive diode controlled oscillator frequency shift keying circuit
US3961285A (en) * 1971-09-23 1976-06-01 International Telephone And Telegraph Corporation Voltage controlled oscillator driver
US3886485A (en) * 1972-11-25 1975-05-27 Victor Company Of Japan Linear voltage controlled oscillator including a timing capacitor charged and discharged through current mirror circuits
JPS5717533Y2 (fr) * 1976-02-27 1982-04-13

Also Published As

Publication number Publication date
DE3265879D1 (en) 1985-10-03
EP0078653A1 (fr) 1983-05-11
JPS6338788B2 (fr) 1988-08-02
JPS5873286A (ja) 1983-05-02
US4531155A (en) 1985-07-23

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